1. Field of the Invention
The present invention relates generally to ratchet tools and the ratchet mechanisms therefor and, more specifically, to the toothed portions of the ratchet mechanisms.
2. Description of the Prior Art
Ratchet tools, such as wrenches and the like, are well known and typically include a gear member disposed for engagement with one or more pawls. The gear member may be arranged as either an internal or external gear, typically a spur gear. The present invention has particular application to ratchet mechanisms of the type which utilize internal gears, with the pawl mechanism being disposed inside the gear. Such mechanisms are disclosed, for example, in U.S. Pat. No. 4,765,449 to Peters and U.S. Pat. No. 5,537,899 to Dietrich, the former disclosing a manually-operated ratchet wrench, and the latter disclosing a power-operated ratchet wrench. In both cases the ratchet mechanism is of a dual-pawl configuration, although it will be appreciated that similar mechanisms utilizing a single pawl are also known. While the following discussion will be fundamentally in the context of ratchet mechanisms of the types disclosed in the aforementioned patents, this is simply for purposes of illustration, and it will be understood that the present invention and the fundamental principles thereof have application to ratchet tools and ratchet mechanisms generally.
In such prior ratchet tools, the gear and the pawls are typically formed from forged blanks with the teeth being broached on the parts. The parts must then undergo further machining and other finishing processes, resulting in high manufacturing costs. Furthermore, the broaching may leave broach "drag" marks on the finished parts, which can cause surface imperfections.
In any ratchet tool, particularly power tools, the toothed parts are, by the nature of the ratchet operation, subjected to high wear. Thus, these parts are typically designed as replacement items, particularly in the case of power tools. This tends to increase the overall cost and inconvenience of operation of the tool to the end user.
Furthermore, in ratchet tools of the type disclosed in the aforementioned patents, the ratchet head or gear essentially "floats" around the drive body which carries the pawls, and is supported by the working action of the pawls, which are located approximately 180.degree. apart. This "floating" action allows the ratchet head to move off center and thereby allows greater or lesser engagement of the pawl teeth with the ratchet gear teeth. This action tends to accelerate wear of the components and aggravates self-reversing or lock-up caused when the teeth on the pawl do not properly engage the gear teeth. In this event, one pawl may snap to the opposite position and thus allow the pawls to oppose each other and prevent operation in either direction. This tendency to self-reversing or lock-up is not only a great inconvenience to the user, but leads to excessive warranty costs. In the tool of U.S. Pat. No. 5,537,899, pawl-end positioning pins have been added to alleviate the tendency to lock-up. But this complicates the construction and assembly and does not cure the "floating" action and resulting imbalance which aggravate the tendency to excessive wear of the toothed parts.